The present invention relates to a device for gauging and verifying the precision of surgical instruments. More particularly, the present invention relates to a calibration system for computer-assisted surgery that accounts for deviations in surgical instrument dimensions from predetermined values.
The medical sciences have been revolutionized through the widespread introduction of digital imaging technologies such as ultrasonography, computer-assisted tomography (CT scanning), and magnetic resonance imaging (MRI). Especially in orthopedic and traumatologic applications, three-dimensional visualization employing these image-acquisition systems has become an important tool for physicians.
Advances in three-dimensional imagery applications have now been deployed in pre-operative, operative, and post-operative settings, providing practitioners with a variety of tools for simulation and/or computer-assisted guidance of medical procedures tailored to the actual anatomy of a given patient. For example, computer-based rendering of bone geometryxe2x80x94such as contours and volume characteristicsxe2x80x94as well as bone surface features can provide the surgeon with a visual representation of an injury to a bone or joint. Such renderings can provide valuable insight with respect to strategies for invasive surgery. Furthermore, the three-dimensional imaging systems can provide a means for simulating surgical procedures, such as the virtual manipulation of bone sections. The simulations may also be useful in the shaping of bone and joint implants, or other anatomical modeling applications.
Three-dimensional imaging technologies have been introduced primarily for pre-surgery simulation and for computer-assisted navigation of surgical instruments with respect to a patient during surgical procedures. Particularly in applications involving the latter, it is desirable to precisely determine the position and orientation of the surgical instrument relative to a spatial reference system. The introduction of an accurate surgical aid of this type to an operating room setting advantageously allows a surgeon to dynamically observe the position of a surgical instrument with respect to a patient. Through the use of a computer processor, monitor, and an appropriate software module, it is possible to predict and display intended trajectories for surgical instruments, in real time, as a function of the instruments"" current orientations. Thus, surgical instruments may be precisely positioned without extensive preoperative planning. However, the guidance software can also allow the surgeon to compare an instrument path that was planned prior to an operation with the current position of the instrument, as well as the path resulting from that instrument position and orientation at any given time. Thus, in practice, an instrument path planned prior to surgery may be followed during surgery to guide the movement of an instrument.
A vast array of surgical instruments can be adapted for computer-assisted surgery, including without restriction such common tools as drills, spoons, scissors, forceps, and probes. In order to facilitate the detection of an instrument""s position in a three-dimensional coordinate measuring system, the instrument is provided with markers or sensors for emitting or receiving electromagnetic waves, sound waves or magnetic fields. Each of these approaches to registering positional data presents limitations or challenges to achieving repeatable and thus reliable accuracy. Ultrasound measurements, for example, may be undertaken in an air environment, and thus are subject to changes in the physical characteristics of air which show significant variation as a function of temperature, pressure and relative humidity. Thus, when using ultrasonic registration, such external factors must be constantly measured so that deviations in the measurements may be continuously compensated. Without this monitoring, significant positioning errors may occur. Such compensation for external factors that effect registration is also necessary for magnetic-field measurement. For example, adjustments may be required to account for interference fields emanating, for instance, from display monitors, computers or electric motors, as well as non-permeable materials in the magnetic field such as metal objects moving within the magnetic field.
Systems for medical diagnosis and treatment that use reference field transducers and medical probes with probe field transducers to detect the position, orientation, or both of the probe within the body of a subject are disclosed in WO 97/29683 to Acker et al. A device that incorporates a frame which can be firmly aligned with an operating table is provided with fiducial gauging receptacles for a surgical probe. Markers are attached to a probe and the frame, and the frame can be locked in position relative to a patient. Provisions are included for transmitting, for example, a magnetic field between the markers on the probe and those on the frame. Sensors are used to detect any such field, and a processor is used to process the detected-field data and determine the position of the probe relative to the markers on the frame. The frame includes catheter calibration receptacles, positioned in known locations relative to transducer mounts. Before a probe carrying catheter is inserted into the body of a subject, the catheter is calibrated by placing the distal tip thereof, which carried the probe, in each of the receptacles in turn, and comparing the respective known position of the receptacle with position information derived from signals generated by position information generating means in the catheter. The drawback of this earlier design lies in the fact that the gauging receptacles can be used for one single probe only.
There is a need for a device for the precise gauging and accuracy verification of surgical instruments. In particular, there is a need for a device that can detect any deformation or wear of surgical instruments by a comparison with factory calibration. More particularly, there is a need for a device that can detect my change in the length of a surgical instrument such as a needle or drill bit.
The invention relates to a device for gauging and verifying the precision of instruments comprising a holder, at least one instrument having a first set of dimensions upon manufacture and a new set of dimensions following use, and a carousel having at least one cavity configured and dimensioned in the shape of the at least one instrument. The carousel is rotatably coupled to the holder. At least two of the holder, the carousel and the instrument are fitted with markers or sensors for emitting or receiving signals for determining spatial information thereof. The spatial information is calibrated by inserting the at least one instrument in its respective cavity in the carousel and determining any change in dimensions from the first set of dimensions to the second set of dimensions.
Preferably, the carousel is rotatably coupled to the holder with a longitudinal member, and the device can include a computer processor for processing and calibrating the spatial information. The spatial information can be positional and orientational data.
In a preferred embodiment, the signals are electromagnetic waves. The signals can be generated by optical light sources, light emitting diodes, or infrared light emitting diodes. The signals also can be carried by fiber optics illuminated by a light source. In other preferred embodiments, the signals can be acoustic waves or magnetic fields.
The invention also relates to a method for gauging and verifying the precision of instruments, the method including the steps of: providing at least one of a holder and carousel, and at least one instrument with markers or sensors for emitting or receiving signals; inserting the at least one instrument in a carousel having at least one cavity, the cavity precisely configured and dimensioned in an as-manufactured shape of the at least one instrument so that the instrument in its as-manufactured shape is disposed at a first spatial location; rotatably coupling the carousel to a holder; determining a new spatial location for the at least one instrument in the cavity; comparing the first spatial location with the new spatial location to determine any change in dimensions of the instrument from the as-manufactured shape; and generating calibration data to account for the change in dimensions.